Conventionally, the stator assembly of an electrical machine has a stator core formed of a stack of steel laminations. As an alternative to the use of steel laminations, the stator core may be formed from iron powder, as exemplified by U.S. Pat. No. 4,947,065 disclosing a stator moulded in one-piece, and by International Patent Application WO95/12912 disclosing a stator comprising a plurality of separate and substantially identical parts.
By its very nature any compacted, non-sintered material will not be fully dense. This means that soft iron powder currently available will have permeabilities that are lower than the permeabilities obtainable with steel laminations. However, magnetic powder composites could offer advantages such as isotropic magnetic behaviour, reduction in iron losses at high frequencies, improved thermal characteristics and flexible design and assembly.
The use of a single tooth geometry could give rise to large benefits when it comes to thermal and manufacturing properties of electrical machines. However, for an induction machine, the single tooth winding can result in a reduced performance due to increased content of MagnetoMotive Force (MMF) harmonics compared to a traditional distributed overlapping winding design.
The patent application SE 9801401-2 discloses an induction machine stator with a single tooth geometry that is arranged to reduce higher order MMF harmonics. These higher order harmonics couples to the rotor and result in increased losses, parasitic torques, etc. Said stator reduces harmonics, but can result in a reduction of performance compared to the traditional distributed overlapping winding design.